Repeater.



1.1. COMER.

REPEATER.

APPLlCATiON FILED MAR. 25, 1911.

Patented Dec. 12, 1916.

3 3HEETSSHEET 1.

imam/70H.-

1.]. COMER.

REPEATER.

APPLICATION HLED MAR. 25. 19H. 1,208,296. Patented Dec.12,1916.

' 3 SHEETSSHEET 2.

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14 TTORNE P UNITED STATES PATENT OFFICE.

JOHN 3'. 00m 0] CHICAGO, ILLINOIS, ASSIGNOR 'IO AUTOMATIC ENUNCIATOR comm, OF CIHCAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

Specification of Letters Patent.

Patented Dec. 12, 1916.

Application filed larch 85, 1911. Serial No. 618,881;

To all whom it may concern Be it known that I Jomz J. Com, a citizen of the United States of America, and resident of Ghica 0, Illinois, have invented a certain new an useful Im rovement in Repeaters, of which the following is a specification.

My invention relates to repeaters of that character in which a microphone is operated by an electro-magnet.

The object of my invention is to provide an im roved construction and arrangement where y no mechanical connection is necessary between the microphone and the magnet.

To this and other useful ends my invention contemplates a repeater in which the microphone is operated by the alternate compression and rarefaction of an inclosed body of air, preferably through the medium of a diaphragm that forms one wall of the sealed chamber in.which said body of air is inclosed, and by means of a connection between the said diaphragm and the armature of the magnet.

In the accompan g drawings-Figure 1 is a plan view 0 a repeater embodying the principles of my invention. Fig. 2 is a side elevation of the repeater shown in Fig. 1. Fig. 3 is a front elevation of the said repeater. Fig. 4 is a rear or inside elevation :of the microphone of said repeater, being a section on line 44 of Fig. 2. Fig. 5 is a section on the same line in Fig. 2, looking in the o posite direction. Fig. 6 is an enlarge sectional view showing the difl'erent parts of the microphone separated. Figs. 7 and 8 are fragmentary sectional views showing details of construction. Fig. 9 is a side elevation of the repeater with the casing on. Fig. 10 is an enlarged longitudinal section of the repeater and casing shown in Fig. 9.

As thus illustrated, my invention comprises a permanent magnet A having a polepiece a secured between the two parts thereof, which pole-piece extends to a point about even with the lower pole a of said magnet. A winding a is mounted on the said polepiece a to form an electro-magnet the core of which is polarized by the other pole at of the permanent magnet. The pole at has a shoulder a on its end which su ports the;

ma et. The magnet structure is held or tie together by the bolt a that asses downward through the posts thereo and through the two bracket arms a and a? which embrace the said structure. The metal cup B is suitably secured to the ends of said'bracket arms, and insulated therefrom, and carries a diaphra C between the rubber packing rings 0 inside thereof. This diaphragm has a stem 0 that engages the lower end of a lever c, the upper end of which latter is supported in the lower end of the screw 0 in the lever a pivoted 'on the upper bracket arm. This lever is pivoted on a screw 0", which extends horizontally through the arm a whereby the lever a may be rocked to move the upper or fulcrumed end of said lever 0 toward or away from the diaphragm to regulate the air gap of the armature. The lever c is rocked by raising or lowering its outer end by means of a screw 0 and a spring 0" on the upper bracket arm. The link a connects the middle of the lever c with the upper end of the armature.

The microphone D comprises a back plate 03 and a front plate d suitably secured together and to the perimeter of the cup B, which latter has a large opening I; at the center thereof. An electrode diaphragm d, of carbon or other suitable material, is interposed and clamped between the plates d and d, and insulated therefrom, with masses of granular carbon d and d at opposite sides thereof in the central cavities of said front and back plates. These masses of carbon are held in place by the front andback electrodes d and d, which are secured by cover plates d and d to the plates (1 and d, respectively, and which are preferably of carbon. In their respective cavities these masses of carbon are encircled by fiufiy asbestos d and d, or other suitable material, which bears upon the diaphragm to prevent leakage of the carbon. This, however, does not interfere with the vibration of the diaphragm, there being spaces or shallow chambers d and d" at each side of the diaphragm for this purpose. The space d communicates with the atmosphere through openings d in the front plate, and the openings d in the back plate serve to connect the lower end of the armature a of t e electro-lal h b d ith th space b t th b k phragms.

plate and the diaphragm 0, there being, in this way, a fully inclosed body of air between the t'wo diaphragms. With this construction a vibration of the diaphragm C will cause an alternate compression and rarefaction of the air between the two dia- This in turn will cause the diaphragm d to vibrate in synchronism with the outer diaphragm, thus repeating 1n the circuits of the differential microphone the electrical vibrations or impulses received in the electro-magnet. The magnet structure and the diaphragm C combine to form a reproducing instrument, and the vibrations of said diaphragm are communicated pneumatically to the microphone. Thus no mechanical connection is'necessary between the microphone and the magnet. The transmission by this method is smooth and pure and highly satisfactory.

The connection between the magnet armature and the diaphragm C is regulated by the screws 0 and 0*. The screw 0 changes or raises the leverage of the lever 0 in accordance with the stiflness of the diaphragm G, and the screw 0 regulates the air gap ofthe armature, as previously explained.

The entire repeater may be inclosed 1n a casing E of any suitable character.

It is an important consideration of my,

invention that the confined body of air between the two diaphragms C and d be not large in volume, as I find that with a slight volume of air better results are obtained. It is also important that the air which is in direct contact with the diaphragm cl be in the form of a thin layer, as this, Ifind, gives better results than when the body of air at this point is of considerable depth and thickness. Again, it will be seen that the body of air in contact with the inner surface of the diaphragm C is in the nature of a thin layer, as this is also desirable. The two thin layers of air are simply connected by the circle of holes d, whereby the alternate compression and rarefaction of one thin layer of air is immediately communicated to the other thin layer, which latter is in direct contact with the diaphragm of the microphone. Natural leakage around the different parts can be depended upon to maintain the said confined body of air at atmospheric pressure. Such leakage, however, will not in any way interfere with the efficiency of the confined body of air as a medium of transmission between the magnet mechanism and the microphone mechanism. There is another advantage in the use of the pneumatic transmission between the magnet mechanism and the microphone, which is this: When the screws 0 and c are adjusted to regulate the armature and connections thereof, the microphone is not in any way disturbed. In other words, the magnet mechanism can be regulated in any desired manner without in any way disturbing or affecting the normal condition of the microphone.

What I claim as my invention is:

1. In a repeater, a differential microphone, provided with a central diaphragm electrode, a reproducing instrument provided with means for pneumatically operating said diaphragm, means for adjusting said diaphragm operating means with respect to said diaphragm, and means for adjusting said operating means independently of said diaphragm.

2. In a repeater, a microphone provided with a central diaphragm electrode, granular carbon at each side of the center of said diaphragm, a shallow chamber for air encircling one body of carbon, said diaphragm serving as one wall of said chamber, a second diaphragm for alternately compressing and rarefying the air in said chamber, to vibrate the first diaphragm, an electro-magnet provided with an armature, a connection between said armature and said second diaphragm, means for regulating said connection, to relatively adjust the diaphragms, and means for re lating the armature independently of said connection.

3. In a repeater, a diaphragm, a variable resistance box covering the middle. portion of one side of said diaphragm, a ring lying in close proximity and substantially covering the exposed surface on the same side of said diaphragm, a second diaphragm so located that the vibrations of said second diaphragm will pneumatically operate said first diaphragm, an electromagnet, and adjustable connections from the armature of said electromagnet to said second diaphragm.

4. In a repeater, a pair of diaphragms forming a closed air space between them, a variable resistance box mounted on each side of and covering the central portion of one of said diaphragms, a ring lying adjacent to one side of said last-mentioned diaphragm and substantially covering the exposed portion thereof, an electromagnet, and connections from the armature of said electromagnet to the other of said diaphragms.

5. In a repeater, a pair of diaphragms forming a closed air space between them, a variable resistance box covering the central portion of one of said diaphragms, a ring lying adjacent to one side of said last-mentioned diaphragm and substantially covering the exposed portion thereof, an electro magnet, and connections from the armature of said electromagnet to the other of said diaphragms, said connections consisting of a lever pivoted at one end, a link connecting the opposite end of said lever to said other diaphragm, and a connection from an intermediate point on said lever to said armature.

6. In a repeater, a pair of diaphragms forming a closed air space between them, a variable resistance box covering the central portion of one of said diaphragms, a ring lying adjacent to one .side of said last-mentioned diaphragm and substantially covering the exposed portion thereof, an electro-' magnet, connections from the armature of said electromagnet to the other of said diaphragms, said connections consisting of a lever pivoted at one end, a link connecting Witnesses R. KEABNS, S. Lnwrs. 

